There is a wonderful page in the Stackoverflow blog which illustrates the spectrum from objective to subjective questions, and notes that the expertise we want to capture usually falls between those extremes.
There are bad questions which need to be closed immediately, but too often good subjective questions in chess.se are closed on the grounds that they are "opinion-based" because "this is not a discussion site".
I think this is a distortion of the principles of stackexchange, and chess.se is greatly impoverished as a result of the current policy. Chess skill is not about objective tablebases, it is about experience & judgement. As the diagram on the Stackoverflow page shows, expertise lies between objective & subjective knowledge.
In moderator posts in chess.se, I see "experience, judgement & expertise" diminished as "opinion", and if it's merely opinion, well of course we can close it off. This is frankly awful, yet it happens many times.
Today's example is Please comment on my book idea, this is basically some trying to sanity-check the scope of a book he plans to write (and yes let me add before someone else does, he is also possibly trying to get a tiny amount of publicity). That seems a worthwhile thing to do. It may be that the question could be rephrased to give more focus, but if that's the case, then the question-closer can provide an example of this focus, rather than requiring the questioner to guess.
There are 6 questions given on the Stackoverflow page as to whether a subjective question is good. I think this question passes all 6 comfortably.
I am grateful for the thankless work of the moderators, but we need to recognize a process problem. It is the act of a moment for 1 moderator to unilaterally close a page, currently with no real effort or reaching out to the questioner to indicate how the question should be fixed. I'm not particularly getting at any moderator but it's a known bug in the process that the moderator cannot just "vote" for closing. The moderator can only close unilaterally, which puts them in an invidious position. Once closed, it takes the concerted action of 5 individuals to reopen a page: it is so inefficient.
How can we fix this broken process? At the very least, I would like before closure of a possibly good-subjective question for the moderator to provide a warning comment containing the scope of needed repairs. That gives the questioner a chance to understand what's going on, and spares other members the large process effort required to re-open the question later.
I want to see moderators using words like "judgement" & "experience". Right now, all I see is the pejorative distorting term "opinion". Until I see these other terms appear in moderator assessment, I have to suspect that sadly there is maybe also a problem of attitude. Attitude cannot be fixed by just process. I would request that some be kinder and more open to good subjective questions, as prevails in the rest of stackexchange. Chess.se will be the richer for this.
Thank you for your time.